sed substitution in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of sed substitution with global flag

What is the output of this command when run on the input string apple apple apple?

Linux CLI

echo "apple apple apple" | sed 's/apple/orange/g'

A

orange apple apple

B

orange orange orange

C

apple orange apple

D

apple apple orange

💡 Hint

The g flag means replace all occurrences in each line.

The s/apple/orange/g command replaces every 'apple' with 'orange' in the input line.

💻 Command Output

intermediate

Effect of sed substitution without global flag

What is the output of this command when run on the input string banana banana banana?

Linux CLI

echo "banana banana banana" | sed 's/banana/grape/'

A

banana banana grape

B

grape grape grape

C

grape banana banana

D

banana grape banana

💡 Hint

Without the g flag, only the first match is replaced.

The s/banana/grape/ command replaces only the first 'banana' in the line.

📝 Syntax

advanced

Identify the correct sed substitution syntax

Which option shows the correct syntax to replace all occurrences of cat with dog in a file named pets.txt?

A sed 's/cat/dog/g' pets.txt

B sed s/cat/dog/g pets.txt

C sed "s/cat/dog/g" pets.txt

D sed -s 'cat' 'dog' pets.txt

💡 Hint

The substitution command should be enclosed in single quotes with the s///g format.

Option A uses the correct syntax with single quotes and the substitution command.

💻 Command Output

advanced

Output of sed substitution with special characters

What is the output of this command?

Linux CLI

echo "path/to/file" | sed 's/\//-/g'

A

path/to/file

B

path-to/file

C

path\to\file

D

path-to-file

💡 Hint

The slash character is escaped to be replaced by a dash globally.

The command replaces all slashes '/' with dashes '-' in the input string.

💻 Command Output

expert

Result of sed substitution with capture groups and backreferences

What is the output of this command?

Linux CLI

echo "2024-06-15" | sed 's/\([0-9]\{4\}\)-\([0-9]\{2\}\)-\([0-9]\{2\}\)/\3\/\2\/\1/'

A

15/06/2024

B

06/15/2024

C

2024/06/15

D

15-06-2024

💡 Hint

Backreferences \1, \2, \3 refer to year, month, day respectively.

The command rearranges the date from YYYY-MM-DD to DD/MM/YYYY format using capture groups.